Add stderr to ifconfig error message

Author: Sebastian Holmin

test/test-manager/src/tests/tunnel_state.rs

@@ -46,8 +46,9 @@ fn set_bridge_interface_mtu(
         let output = cmd.output().context("Failed to execute ifconfig")?;
         if !output.status.success() {
             bail!(
-                "ifconfig failed with status: {}",
-                output.status.code().unwrap()
+                "ifconfig failed with status code {}: {}",
+                output.status.code().unwrap(),
+                String::from_utf8(output.stderr).expect("Parse stderr as utf-8"),
             );
         }
         Ok(())